What should be checked before relying on a WPI figure?
Check maximum medical improvement, the body area, objective findings, the NSW Guideline chapter and any NSW modification before relying on a percentage.
Can this page calculate your percentage?
No. WPI depends on an assessor, maximum medical improvement, objective findings and the NSW Guidelines. This page is general information only.
Permanent impairment assessment
How permanent impairment is assessed for ACL, PCL, MCL, LCL tear, reconstruction and residual laxity
Knee ligament WPI turns on objective residual laxity and stable function at MMI. ACL, PCL, MCL or LCL reconstruction is important treatment history, but reconstruction alone is not a percentage if no ratable laxity remains.
What injuries can happen to this body part?
- ACL tear or reconstruction after pivoting, sport-like movement, fall or work twist
- PCL injury after dashboard-type impact, fall or direct blow
- MCL or LCL sprain/tear with valgus or varus instability
- Combined ligament injury with meniscal or cartilage damage
Symptoms and findings that matter
- Which ligament is injured and whether laxity remains at MMI
- Clinical instability testing and comparison with the opposite knee
- Whether MRI/operative findings match the clinical instability
- Whether meniscus, cartilage, arthritis or replacement issues are separate and validly combinable
- Whether giving-way symptoms reflect objective laxity, pain inhibition, weakness or fear of movement
What investigations are usually relevant?
- Treating specialist report and final impairment assessment at maximum medical improvement
- Imaging, pathology, audiology, ophthalmology, respiratory, nerve or functional testing that fits the body system
- Operative reports, discharge summaries, rehabilitation records and objective clinical measurements where relevant
How WPI is assessed for this body part
- Knee ligament WPI turns on objective residual laxity and stable function at MMI. ACL, PCL, MCL or LCL reconstruction is important treatment history, but reconstruction alone is not a percentage if no ratable laxity remains.
- Assessment source: NSW Guidelines Chapter 3 paragraph 3.26, which adds an omitted mild cruciate/collateral ligament laxity row at 5% WPI (12% lower extremity impairment), plus adopted AMA5 diagnosis-based methods where otherwise applicable.
- The assessor should explain maximum medical improvement, the body-system chapter, the method selected, any NSW modification, and why the objective findings fit that method.
How movement affects the assessment
- Ligament injuries can affect stairs, pivoting, ladders, kneeling and uneven ground.
- ROM may matter, but instability/laxity is a separate question and should not be confused with pain-limited movement.
NSW ligament laxity and knee instability rows
Mild cruciate or collateral ligament laxityNSW adds the omitted mild category: 5% WPI (12% lower extremity impairment), where clinical laxity criteria apply.
Reconstruction aloneACL/PCL/MCL/LCL reconstruction does not create WPI by itself; residual laxity and function at MMI matter.
Instability vs symptomsGiving way, fear of movement or pain should be separated from objective ligament laxity, meniscus locking and arthritis/cartilage loss.
Meniscus diagnosis-based examples where AMA5 is adopted
Partial medial or lateral meniscectomy1% WPI (2% lower extremity impairment) where the adopted AMA5 diagnosis-based estimate applies.
Total medial or lateral meniscectomy3% WPI (7% lower extremity impairment) where the adopted AMA5 diagnosis-based estimate applies.
Partial medial plus partial lateral meniscectomy4% WPI (10% lower extremity impairment) where the adopted AMA5 diagnosis-based estimate applies.
Total medial and lateral meniscectomy9% WPI (22% lower extremity impairment) where the adopted AMA5 diagnosis-based estimate applies.
Not scan-onlyA meniscal tear on MRI does not equal the meniscectomy row if no meniscectomy or qualifying residual condition is present.
NSW arthritis and cartilage-loss rules
Cartilage loss definitionOsteoarthritis for lower limb WPI is assessed as cartilage loss, usually through radiologically determined joint-space intervals in AMA5 Table 17-31 as adopted by NSW.
Knee compartmentsThe knee has three compartments. The major impairment compartment is used; compartments are not added or combined.
Cannot combine with some methodsArthritis rating cannot be combined with gait disturbance, muscle atrophy, muscle strength or ROM.
Patello-femoral cautionPatello-femoral arthritis/crepitus is not added again when assessing arthritis of the knee joint itself.
Resurfacing proceduresNSW gives no additional impairment for resurfacing procedures for localised cartilage lesions or defects in major joints.
NSW lower limb global rules
Most specific method firstUse the method that most specifically addresses the lower limb impairment where possible, rather than a broad fallback label.
Highest valid assessmentWhere more than one valid lower limb method applies, the NSW Guidelines generally require the assessment that gives the highest valid rating, unless a specific rule prevents it.
Do not exceed amputation valueA lower limb part or region cannot exceed the applicable amputation value. The whole lower limb maximum is 40% WPI, except where a specific gait table gives WPI directly.
Gait derangement is last resortGait derangement should be used only as a last resort and cannot be combined with other lower extremity assessment methods.
Permanent walking aid onlyIf a walking aid is relied on, the evidence should show permanent use, not a temporary aid during treatment or recovery.
ROM reliabilityROM can be unreliable where effort, pain behaviour or inconsistency affects measurement. The opposite side should be compared where relevant.
Arthritis needs imagingArthritis/cartilage loss must be radiologically assessed. Pain, crepitus or a broad MRI comment is not enough by itself.
Practical WPI examples
- A reconstructed ACL with stable testing may not fit a laxity row simply because surgery occurred.
- Mild cruciate or collateral ligament laxity has a NSW-added row of 5% WPI where the clinical criteria apply.
- Combined ACL and meniscus injury needs a double-counting check before adding diagnosis-based estimates.
Evidence checklist
- A clear diagnosis and the body area being assessed
- Records showing the condition has reached maximum medical improvement, if that is the issue
- Specialist reports, imaging reports and treating notes relied on by the assessor
- Objective findings on examination, not only symptoms described by the injured person
- A work and treatment chronology explaining the injury, treatment, surgery and recovery path
- Any previous injury, degeneration, congenital issue or non-work cause that needs apportionment considered
- MRI
- Operative report
- Lachman/drawer/varus-valgus testing
- Orthopaedic review
- Physiotherapy progress
- Work-duty evidence involving ladders, stairs, kneeling or uneven ground
What usually does not increase WPI
- Assuming a scan result automatically gives a WPI percentage
- Confusing pain, disability or inability to work with permanent impairment
- Ignoring maximum medical improvement before arranging an assessment
- Using an AMA5 table without checking whether the NSW Guidelines modify or replace it
- Double counting the same impairment through two methods when the Guidelines require one method
- Saying reconstruction equals WPI
- Ignoring stable post-operative testing
- Combining laxity with gait or arthritis without checking the table rules
Assessment source
Assessment source: Assessment source: NSW Guidelines Chapter 3 paragraph 3.26, which adds an omitted mild cruciate/collateral ligament laxity row at 5% WPI (12% lower extremity impairment), plus adopted AMA5 diagnosis-based methods where otherwise applicable.
This section is source-backed general information. It is not a WPI assessment and is not legal advice.
- SIRA NSW Workers Compensation Guidelines for the Evaluation of Permanent Impairment: Source for the NSW assessment framework, MMI, AMA5 adoption, NSW modifications and exclusions.
- SIRA lower extremity chapter: Source for NSW lower extremity assessment rules, gait derangement limits and NSW-modified lower limb tables.
Related injury and claim pages
Need a practical claim check?
If an impairment percentage, medical assessment or insurer decision is affecting your NSW injury claim, send the decision or report for a practical review. This is general information only and does not guarantee any result.
Request a free claim checkAssessment scope for Knee Ligament WPI Assessment
The assessment scope for Knee Ligament WPI Assessment should be stated precisely before any percentage is considered. The file should identify whether that label describes the primary diagnosed condition, a symptom of another injury, a regional overview or one component of a broader impairment. Findings from another body area or diagnosis should not be transferred without explanation. The report should connect the stated condition to the correct NSW Guideline chapter, objective findings, treatment history and any permitted combination or apportionment method. This distinction is particularly important where similar page labels cover different clinical questions.
- Confirm the diagnosis and body area being assessed as Knee Ligament
- Separate condition-specific findings from overlapping symptoms or injuries in another body area
- Check that the selected NSW Guideline chapter and method match the condition actually assessed
- Explain any combination, apportionment or exclusion rather than relying on the page label alone
Start with maximum medical improvement
Permanent impairment should generally be assessed when the condition is stable and unlikely to change substantially in the next year. Treatment, surgery and rehabilitation history may affect whether the timing is appropriate.
Use the NSW Guidelines first
The NSW Guidelines adopt AMA5 in many areas, but NSW modifications prevail. Do not assume an AMA5 table applies without checking the NSW chapter and any public SIRA clarification.
Keep the assessment practical
A useful assessment file separates diagnosis, objective findings, surgery history, work capacity issues, apportionment questions and the body-area method used by the assessor.
Ask about an impairment issueDocuments and records
Injury evidence to organise early
The useful records depend on how the injury happened, when symptoms were recorded and how treatment or work capacity changed.
- Date, location and short description of the injury event
- Medical certificates, reports, scans, treatment records or hospital documents
- Employer, insurer, police, incident or venue records where relevant
- Photos, witness details, dashcam or other supporting material if available
- Income, superannuation, work capacity or leave records where relevant
- Letters, emails, claim numbers and decisions already received
Common questions
Injury evidence questions
Short general answers only. The right next step depends on the facts, dates and documents.
Is WPI the same as being unable to work?
No. WPI is a medical impairment measure. Work capacity, weekly payments, damages, treatment disputes and TPD issues are separate questions, although the evidence may overlap.
Does pain alone create a WPI percentage?
Not by itself. NSW workers compensation excludes AMA5 Chapter 18 on pain. Chronic pain is assessed through the underlying diagnosed condition where the Guidelines permit it.
Can secondary psychological symptoms be added to physical WPI?
In NSW workers compensation, secondary psychiatric or psychological impairment is not assessed as permanent impairment. Primary psychological impairment is assessed separately and is not combined with physical WPI.
Injury pathway enquiry
Not sure which claim type matches the injury?
Start with how the injury happened, what medical records exist and how work or daily activity has changed. The same injury can sit in different pathways.